function initComputed(vm, computed){
    var watchers = vm._computedWatchers = Object.create(null)
    for(var key in computed){
        var userDef = computed[key]
        var getter = typeof userDef === 'function'? userDef : userDef.get;
        if(getter == null){
            console.warn("Getter is missing for computed property" + key);
        }
        watchers[key] = new watchers(vm, getter, , {lazy: true})
    }
}